Problem: Stephanie ate 1 slice of pie. Luis ate 1 slice. If Stephanie ate $\dfrac{1}{3}$ of the pie, what fraction of the pie was eaten?
If 1 slice represents $\dfrac{1}{3}$ of the pie, there must have been a total of 3 slices. $\text{fraction of pie eaten} = \dfrac{\text{number of slices eaten}}{\text{number of slices total}}$ They ate ${2}$ out of $3$ slices. They ate $\dfrac{2}{3}$ of the pie.